Melt butter in a sauce pan, add garlic and cook until tender and fragrant.

If using flour add it straight to the butter mixture and stir until smooth, then add milk
If using potato starch first whisk it into the cold milk, then add to the garlic mixture
(Corn Starch is an ok substitute for potato starch but it doesnt hold up the thickness quite as well with the lengthy slow cooker cook time)
Cook over medium heat until thickened

Add cheeses and cook , stirring well until they are fully melted. Add Chives, liquid smoke, salt and pepper. Mix well

Pour Cheese mixture over the potato mixture. DO NOT STIR.

Cook on low 6-8 hours, high 4-6 until the potatoes are tender. Stir gently.